A controllable card, such as a smart card, can be programmed or otherwise controlled to perform certain functions when read by a card reader. For example, a card reader may be coupled to a computing device that can allow a user to operate the computing device only in response to a controllable card with the appropriate information on it being received in the card reader. Removing the card, or inserting a card without the proper information, can result in a user being prevented from operating the computing device. For example, the screen of the computing device can lock or change to a black screen in response to the card being removed. Controllable cards can be programmed using software developed to apply security or other functions to the card.